Boa, Emerald Tree

Corallus caninus

Adult length: about 6 ft (1.8 m); coloration: an emerald green ground color with a white irregular interrupted zigzag stripe or so-called ‘lightning bolts’ down the back and a yellow belly; juveniles vary in color between various shades of light and dark orange or brick-red; appearance: large bulky head, thin neck, stout body (can be over 2 in. in diameter) and strong prehensile tail. Pupils are vertically oriented like a cat.

Family

Boidae

Order

Squamata

Class

Reptilia

Range

The Amazon Basin region of Colombia, Ecuador, Peru, northern Bolivia, Brazil, and from Venezuela to Surinam and the Guianas (or Northern Shield Forests)

Habitat

Life Expectancy

Sexual Maturity

Females – 4 to 5 years; males 3 to 4 years

Diet

In the wild, they eat small mammals, small birds, lizards and frogs; in the Zoo, they are fed rodents.

Status

Not listed

Behaviors

A strictly nocturnal and arboreal species. It spends its days in a characteristic coil over a tree branch with its head perched at the center. At night, it will remain coiled on its branch, extending its head downwards and curled as if about to strike. It will hold still in this position, waiting for prey to approach directly below. Prey is grasped with the long frontal teeth, pulled into the coils and constricted to asphyxiation. Due to the extremely slow metabolism of this species, it feeds much less often than ground dwelling species and meals may be several months apart. Its main predators are eagles (Guianan Crested Eagle and Harpy Eagle). Previously, it had been thought that the primary diet consisted of birds. However, studies of the stomach contents of this species indicate that the majority of its diet consists of small mammals. Juvenile and neonates have also been known to feed on small lizards and frogs, particularly glass frogs. Breeding occurs from February to April. Females are ovoviviparous (retaining eggs inside the body and then appearing to give birth to live offspring when they hatch), producing an average of 6 to 14 young at a time after a gestation period of 250 days or longer. Litters exceeding these numbers are extremely rare. Young are given no maternal care and fend for themselves. At four months of age they start to develop the adult green coloration. These boas live solitary lives except when mating.

Adaptions

The emerald tree boa’s body is compressed laterally, which allows it to press close to the tree branches. Long powerful fore-teeth enable tree boas to penetrate the feathers of birds and hold on to them; in fact they are an advantage in holding any prey to keep it from dropping to the ground. Heat sensing labial pits located on the upper lip aid in detecting potential food or predators. Like other snakes, they also use their tongues, Jacobsen’s organ and body to sense chemical cues and detect vibrations. Theories to account for juvenile coloration being different from adults is that they may inhabit a different environmental niche from the adults (low bushes) and/or they mimic the arboreal multicolored vipers of Central and South America which helps against predation. As they mature they turn to camouflage instead of mimicry. The emerald tree boa uses the “concertina” method of tree climbing. It holds on to the trunk with its tail and lower part of its body, reaches up with its head and hooks its neck around the trunk. Then it releases its hold with the tail and pulls the rear part of its body up to the level of the neck.

Special Interests

The genus name Corallus means “of coral” or “coral-like”, and it was used by Linnaeus to describe the coral-like pattern of this snake. The species name caninus has been applied because the posterior bulges on the head and angled snout cause it to resemble the profile of a dog. In addition its elongated maxillary teeth look like the canine teeth of a dog. Transliterated, the name Corallus caninus actually means “coral-like snake with a head resembling that of a dog”. This boa is a primitive snake with two lungs and the remnants of a hip girdle. There are two distinct types or locales of Corallus caninus: the Surinam variant, also known as the Guyana Shield Emerald Tree Boa and the Amazon Basin Emerald Tree Boa, known as the ‘Amazon Basin’ variant. The Northern variant is found primarily in Northern regions of South America. The ‘Basin’ variant’’, as the name suggests, is only found along the basin of the Amazon River, in Southern Surinam, southern Guyana, southern Venezuela to Colombia, Peru and Brazil and in the surrounding jungle of the Amazon River. It is quite likely that, in time, Corallus caninus will be split into 2 subspecies: Corallus caninus caninus (Shield variant) and Corallus caninus braziliensis (Basin variant). There are striking differences between the two locales in the way of coloration, scaling, pattern and markings and temperament. The Northern variant is a smaller animal than the Amazon Basin variant and has a lighter green coloration with white dorsal markings that do not connect, as in the Amazon Basin variant. The ‘Basins’ also have a very yellow belly and much smaller snout scales.

Folklore

Conservation

All rain forest species’ survival is threatened by habitat loss and degradation. Emerald tree boas have also become very popular in the pet trade. Although commercial trade has not adversely impacted their numbers in the wild, it has the potential to deplete numbers at an unsustainable level if not kept in check.